<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <!--    视口，调整页面适应移动端
                width=device-width：页面宽度与设备宽度一致
                initial-scale=1：初始缩放为1，即不会缩放
                minimum-scale=1：最小缩放比
                maximum-scale=1：最大缩放比
                user-scalable=no：用户自定缩放
        -->
    <meta name="viewport"
          content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no"/>
    <title>Title</title>
    <link href="../0918/bootstrap/css/bootstrap.css" rel="stylesheet">
    <!--    如下第三方库的JS一般写在head标签中-->
    <script src="../0918/js/jquery-3.5.1.js"></script>
    <script src="../0918/bootstrap/js/bootstrap.js"></script>
</head>
<body>
<div class="dropdown">
    <button class="btn btn-default dropdown-toggle" type="button" id="dropdownMenu111" data-toggle="dropdown"
            aria-haspopup="true" aria-expanded="true">
        Dropdown
        <span class="caret"></span>
    </button>
    <ul class="dropdown-menu" aria-labelledby="dropdownMenu1">
        <li><a href="#">Action</a></li>
        <li><a href="#">Another action</a></li>
        <li><a href="#">Something else here</a></li>
        <li role="separator" class="divider"></li>
        <li><a href="#">Separated link</a></li>
    </ul>
</div>
<div class="btn-group" role="group" aria-label="...">
    <button type="button" class="btn btn-default">Left</button>
    <button type="button" class="btn btn-default">Middle</button>
    <button type="button" class="btn btn-default">Right</button>
</div>

<div class="alert alert-success" role="alert">...</div>
<div class="alert alert-info" role="alert">...</div>
<div class="alert alert-warning" role="alert">...</div>
<div class="alert alert-danger" role="alert">...</div>
</body>
</html>